A common law for the differential rotation of planets and stars

TL;DR

This paper identifies a universal scaling law for differential rotation and zonal flows in planets and stars, supported by observations and simulations, indicating a common underlying mechanism.

Contribution

It reveals a universal $ ext{ extellipsis}$ scaling law for zonal flows across diverse planetary and stellar systems, suggesting a common physical mechanism.

Findings

Zonal flow kinetic energy scales as $ ext{ extellipsis}$ with spherical harmonic degree.

Observed and simulated systems all follow the $ ext{ extellipsis}$ scaling law.

A simple common mechanism likely shapes zonal mean flows across different celestial bodies.

Abstract

All planets and stars rotate. All gas planets in our solar system, the Sun, and many stars show a pattern of east- or westward mean flows. This phenomenon is known as differential rotation in the stellar and as zonal jets in the planetary context. Observations, laboratory experiments and simulations show that the zonal flow kinetic energy scales like $\ell^{-5}$, where $\ell$ is the spherical harmonic degree (which is effectively a latitudinal wave number). Here, we analyze observation of the Sun, as well as simulations of the dynamics in Saturn and in the outer atmosphere of an ultra-hot Jupiter. While these systems are very different, they all develop strong zonal winds that obey the $\ell^{-5}$ scaling. Our results strongly suggest that there is a simple common mechanism that shapes zonal mean flows in planets and stars independent of the flow driving.